<template>
  <div>
    <router-link tag="div" to="/" class="header-abs" v-show="showAbs">
      <span class="iconfont back-icon">&#xe624;</span>
    </router-link>
    <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
      李小龙乐园
      <router-link to="/"><div class="iconfont header-fixed-back">&#xe624;</div></router-link>
    </div>
  </div>
</template>
<script>
export default {
  name: 'DetailHeader',
  props: {
    bannerHeight: Number
  },
  data () {
    return {
      showAbs: true,
      opacityStyle: {
        opacity: 0
      }

    }
  },
  methods: {
    handleScroll () {
      const top = document.documentElement.scrollTop
      if (top > 0) {
        let opacity = top / this.bannerHeight
        opacity = opacity > 1 ? 1 : opacity
        this.opacityStyle = {opacity}
        this.showAbs = false
      } else {
        this.showAbs = true
      }
    }
  },
  activated () {
    window.addEventListener('scroll', this.handleScroll)
  },
  deactivated () {
    window.removeEventListener('scroll', this.handleScroll)
  }
}
</script>

<style lang="stylus" scoped>
@import "~styles/varibles.styl"
  .header-abs
    position absolute
    left .1rem
    top .1rem
    width .72rem
    height .72rem
    line-height .72rem
    color #fff
    text-align: center
    border-radius .36rem
    background rgba(0,0,0,.5)
  .header-fixed
    position fixed
    z-index 2
    left 0
    right 0
    top 0
    height $headerHeight
    line-height $headerHeight
    text-align center
    font-size .32rem
    color #fff
    background: $bgColor
    .header-fixed-back
      position absolute
      top 0
      left .2rem
      color #fff
</style>
